Lighting devices implemented as flexible linear modules are available on the market.
Such devices are available also in a “protected” version, wherein a flexible light engine is embedded into a flexible shield (case) which may be made e.g. of polymer material.
The case protects the light engine from the outer environment, with a minor impact on light output performance.
The related manufacturing processes may involve the lamination on an extruded polymeric profile of an unprotected flexible module (e.g. a board such as a flexible Printed Circuit Board, PCB) carrying various components, such as said light radiation sources, DC/DC drivers, resistors, etc., which may optionally be mounted via SMD technology.
This operation may involve dispensing one or more viscous polymers (e.g. adapted to act as a glue/sealant once cured), optionally in the context of a reel-to-reel process, the laminated products moving on carousels, e.g. with fixed curing ovens, while the components (profiled case and light engine) are moving with respect to the ovens.
In the manufacturing processes envisaging a temperature curing, the need is felt to take into account the different thermal elongations of the flexible lighting module and of the extruded polymeric profile. At least in some cases, an instability may arise in the lamination of the flexible module onto the profile, causing the appearance of waving or twisting along the module.
One way to reduce waving involves the use of a tape sandwiched between the extruded profile and the flexible lighting module, while the assembly comprising the lighting module and the extruded profile undergoes the application of a “potting” material, e.g. a liquid transparent polymer which is subsequently cured, the tape being adapted to absorb the different thermal elongations while curing.
Another possibility involves reducing the module length. If the module length is lower than the length of the curing oven, the flexible module and the extruded profile have no bond at either end, and may therefore slide locally one with respect to the other, in such a way as to absorb the different thermal elongations. A variant consists in achieving the curing of the module via a series of exposures, i.e. in subsequent steps wherein for example a 6 meter long module is processed in 15 subsequent steps, each covering a length of 6/15=0.4 meters.